We propose to conduct further electrophysiological studies on the neural mechanisms of vision. We will investigate the means by which patterns of light and shade imaged on the retina are transduced by the photoreceptors into patterns of neural activity, how the integration of the opposed influences of excitation and inhibition by neural networks in the retina abstract significant information from such patterns of activity, and how this information is then transmitted by the optic nerve to the visual areas of the brain. Our methods will consist of recording the electrical activity of one, or a few, neurons at various levels in the visual system. We will use computer techniques for acquisition of data and for control of stimuli. We will utilize applied mathematics (mainly linear and nonlinear systems analysis) in our analyses of data and in the formulation of quantitative theories of functions of neural networks. Our approach is comparative: We will do electrophysiological experiments on the visual systems of various invertebrates (mainly horseshoe crab) and vertebrates (mainly frog and cat), and we will conduct some related psychophysical experiments on human vision. Our aim is the understanding of integrated visual function in terms of the properties and mechanisms of the cellular units of the visual system, and especially in terms of the interactions among these units.